It is known that bitumen can be produced, in particular, from crude petroleum by distillation and deasphalting of the heavy fraction obtained by such distillation or distillations. Depending on the origin of the crude, bitumen consists of varying proportions of paraffinic oil (aliphatic or naphthenic), aromatic oil, resins and asphaltenes (on this subject, attention is directed to European Patent [EP] 246 956 and its U.S. equivalent, U.S. Pat. No. 4,810,367, both of which are owned by Applicants' assignee and are incorporated herein by reference).
Depending on its composition, bitumen can have a more or less thermoplastic character. It softens on heating, and its softening point, commonly referred to as its "ring-and-ball" temperature after the method of determination used (AFNOR.sup.1 method NFT 66008), can vary from about 30.degree. to about 130.degree. C., depending on the process by which the bitumen was obtained. FNT .sup.1 Association Francaise de Normalisation=French Association for Standardization
These temperatures may be judged as insufficient for certain uses because of:
risk of high temperature flow when used as sealing coatings; PA1 inadequate elastic behavior; PA1 inadequate heat resistance; for instance, in certain cements used for certain applications (automobile chassis). PA1 1. Oxidation of bitumen by air blowing at about 250.degree. C. However, the product thus obtained has disadvantages such as a high "ring-and-ball" temperature and is harder and more brittle. PA1 2. Modification of bitumen by incorporation of certain polymers, which affords products with a "ring-and-ball" temperature as high as 120.degree.-150.degree. C. However, these products have disadvantages such as that at a temperature of 150.degree. C., such products present only slight elastic properties. PA1 3. Modification of bitumen by incorporation of a polymer such as SBR (styrene-butadiene rubber) or SBS (styrene-butadiene-styrene) which can be vulcanized with sulfur (or a sulfur donor) or a peroxide. However, this modification has disadvantages. It requires elevated and accurately controlled temperatures over a relatively long period of time. Further, product thus obtained has a very high viscosity and is not readily compatible with application methods used by the industry. Also, vulcanization imparts to it an irreversible character which is not conducive to easy use. The product must be used within weeks after its production, because its viscosity must remain compatible with that with which it will be used. PA1 a molten bitumen-polymer composition that can be crosslinked with sulfur, PA1 an aqueous phase comprising an emulsifying system, and PA1 a sulfur-generating crosslinking system, is introduced into an emulsification zone and the zone is kept at a temperature from 50.degree. to 160.degree. C. until an emulsion of the bitumen-polymer binder is obtained wherein the polymer is crosslinked into a tridimensional structure. To prevent excessive crosslinking of the polymer and thus an excessively high viscosity of the bitumen-polymer composition, it is recommended to emulsify a blend of the composition and the crosslinking system immediately or soon after the composition is formed. PA1 a) at least one bitumen; PA1 b) at least one polymer having hydrocarbon chains with mobile hydrogens or free electrons, said polymer being grafted and crosslinked in situ in the bitumen through a complex of at least one organic silicon compound, said complex being formed from a primary constituent for grafting an organic silicon compound onto the polymer and a secondary constituent, said secondary constituent being the organic silicon compound, PA1 c) water, and PA1 d) at least one emulsifying agent. PA1 at least one bitumen; PA1 at least one polymer having hydrocarbon chains with mobile hydrogens or free electrons; PA1 at least one organic silicon compound; PA1 a compound for grafting the organic silicon compound onto the polymer; PA1 water; and PA1 at least one emulsifying agent; PA1 at least one bitumen; PA1 at least one polymer having hydrocarbon chains with mobile hydrogens or free electrons; PA1 a complex including a primary constituent for grafting an organic silicon onto the polymer and a secondary constituent comprising: at least one organic silicon or compound; and PA1 at least one emulsifying agent; PA1 wherein the organic silicon compound is grafted onto the polymer and the polymer crosslinked in situ in the bitumen. PA1 a) making a virtually homogeneous molten blend of at least one bitumen and at least one polymer having hydrocarbon chains with mobile hydrogens or free electrons, said polymer optionally first having been dissolved in a solvent, this step a) including the incorporation into the blend, kept in the molten state, of the primary and secondary constituents that bring about the formation of the complex and give rise to the grafting and crosslinking of the polymer, at least one of the secondary constituents being an organic silicon compound, optionally previously dissolved in the polymer solution; PA1 b) keeping the product made in a) in the molten state with agitation for a length of time sufficient to achieve grafting of the complex of the organic silicon compound onto the polymer in the composition made in a); PA1 c) incorporating with agitation into the bitumen-polymer composition obtained in b) an aqueous solution of the emulsifying agent at a temperature sufficient to maintain the bitumen-polymer composition in the molten state, said step c) leading to the formation of an emulsion. PA1 (a) blending in the molten state at least one bitumen and at least one polymer having hydrocarbon chains with mobile hydrogens or free electrons; PA1 (b) adding to the molten blend a grafting agent for grafting an organic silicon compound onto the polymer; PA1 (c) adding to the molten blend an organic silicon compound; PA1 (d) grafting the organic silicon onto the polymer PA1 (e) mixing into the molten blend of step (d) an aqueous solution of an emulsifying agent. PA1 a) the heaviest fraction obtained by straight-run distillation of a crude at atmospheric or reduced pressure; PA1 b) the heavy phase obtained by solvent deasphalting a heavy fraction obtained as in a); PA1 c) the product obtained by oxidation, in the presence or absence of a catalyst, of a heavy fraction as per a) or a heavy phase as per b); PA1 d) the product obtained by oxidation, in the presence or absence of a catalyst, of a blend of PA1 e) a blend of an oxidized product obtained as in b) or c) or of a hard base, and PA1 f) a visbroken base, alone or blended with one of the aforesaid products. PA1 polyolefins such as poly-alpha-olefins or C.sub.1 -C.sub.12 polyolefins, for instance polyethylene, polypropylene, polybutylene, polymers of hexene, polymers of 4-methyl-1-pentene or olefin copolymers, for instance copolymers or terpolymers of alpha-olefins such as C.sub.1 -C.sub.12 alpha olefins, for example copolymers of ethylene and hexene, of ethylene and 4-methyl-1-pentene and the like, PA1 natural or synthetic rubbers, such as PA1 polyvinyl chloride PA1 ethylene-vinyl acetate copolymers. PA1 a) from 29 to 67 wt % of bitumen, PA1 b) from 1 to 13 wt % of crosslinked and grafted polymer, PA1 c) from 69.5 to 18 wt % of water, PA1 d) from 0.5 to 12 wt % of emulsifier, the crosslinked and grafted polymer containing up to 10 wt % of the complex (primary constituent+secondary constituent).
Among the techniques for improving the heat resistance of bitumen are, in particular, the following.
To attempt to circumvent these drawbacks, it has been proposed in Patent Application EP-A-0 467 790 to prepare an aqueous emulsion of a bitumen-polymer binder with a tridimensional polymeric structure. To this end, a blend containing: